CN109621918B

CN109621918B - Amino functionalized porous material and preparation method and application thereof

Info

Publication number: CN109621918B
Application number: CN201811542430.0A
Authority: CN
Inventors: 万德成; 金明; 徐梓雲
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2018-12-17
Filing date: 2018-12-17
Publication date: 2021-07-20
Anticipated expiration: 2038-12-17
Also published as: CN109621918A

Abstract

The invention relates to an amino functionalized porous material, a preparation method and application thereof, wherein the preparation method comprises the following steps: dispersing rigid particles into a water phase containing polyethyleneimine, adjusting the pH to 10-13, adding an oil phase to form an oil-in-water emulsion, adding the oil phase in advance or adding a cross-linking agent after the oil-in-water emulsion is formed, carrying out cross-linking reaction, standing for solidification, deoiling, dehydrating and drying after the reaction is finished, thus obtaining the product. Compared with the prior art, the porous material has higher mechanical strength, can be directly used for adsorbing aldehydes, acid gases, anionic dyes and metal ions, and can also be used as a catalyst carrier.

Description

Amino functionalized porous material and preparation method and application thereof

Technical Field

The invention belongs to the field of materials, and particularly relates to an amino functionalized porous material, and a preparation method and application thereof.

Background

The treatment of air pollution and water pollution puts higher requirements on science and technology. The amino group can adsorb various acidic gases such as sulfur dioxide, carbon dioxide, hydrogen sulfide and the like, and can also adsorb anionic dyes, metal ions and the like. In order to increase the adsorption area and facilitate the treatment, amino groups should be covalently expressed on the porous substrate, but it is difficult to simply and conveniently express active amino groups on the surface of the porous material.

The porous material can provide a higher surface area and a functionalized surface, and can be used in the fields of adsorption, separation, catalysis, water treatment and the like. The preparation of porous materials by using a high internal phase emulsion method is convenient, taking a water-in-oil concentrated emulsion as an example, under the assistance of a stabilizer, a large amount (more than 74 percent of the total volume of the system) of water droplets are dispersed in a small amount of oil continuous phase, and the porous materials can be formed by removing the water droplets after the oil phase is solidified. When the stabilizer of the high internal phase emulsion is a small or large molecule, a porous material is generally obtained, but if a particulate stabilizer is used, the resulting emulsion is called Pickering emulsion, and a closed cell material is generally formed. It is noted that the volume of the dispersed phase is not critical to the formation of the through-pores, e.g., the internal phase emulsion may also form a through-pore material. The formation mechanism is complicated and is considered to be related to the kind and amount of the stabilizer. Concentrated emulsions are typically stabilized with commercially available small molecule surfactants, and after removal of the water droplets, the hydrophilic ends of the surfactants remain aligned toward the surface, forming hydrophilic pores. Such materials are commonly referred to as polyHIPE. This production method is undoubtedly characterized by certain greenness and cheapness, but has two disadvantages that make it difficult to practically use polyHIPE. Firstly, the micromolecule surfactant on the surface active agent is very easy to fall off, and an inert surface is left, and the introduction of a functional group on the inert surface is complicated; and the mechanical strength of the polyHIPE is poor, micron-sized suspended particles are easily formed, and the practical application is difficult.

Post-functionalization on porous substrates is a common strategy but is a multistep and inefficient reaction. Porous materials produced by other methods often suffer from similar deficiencies. For example, silica particles produced by precipitation methods may have a 50% or more reduction in substrate surface area due to the varying surface pore sizes and the blockage of many nanopores after surface modification; the surface coverage of functional groups is often only 30%. In addition, the bond between the substrate and the functional group also requires severe conditions such as acid and alkali resistance to prevent the functional group from falling off. Because the use or regeneration of porous materials often involves strong acid and base treatments. This increases the difficulty of synthesis.

In recent years, macromolecular surfactants have been used instead of small-molecular surfactants, resulting in the direct obtainment of porous materials with permanently functionalized surfaces. The large molecular surfactant is physically adsorbed on the substrate like the small molecular surfactant, but is difficult to be detached because of its high molecular weight and high migration energy barrier, and further, the large molecular surfactant is used in a small amount (sometimes only 1% of the continuous phase) enough to stabilize the concentrated emulsion, which is advantageous. For example, with a great amount of active primary and secondary amines and alkylated polyethyleneimine as an oil-soluble stabilizer, Porous materials with active amino groups on the surface can be directly obtained in the form of Water-in-oil concentrated emulsion (Ye YL, Wan DC, Du J, Jin M, Pu HT. Dendritic Amphicle media Porous for Elimination Organic Micropollutants from Water J. Mater. chem. A.3, 6297-.

The insufficient mechanical properties of porous materials are a general problem, and many attempts have been made to use some specific monomers, or to oleophilize the mechanical reinforcing particles as additives in water-in-oil systems, and to control the uniformity of crosslinking. So far, a scheme with high universality, great improvement and acceptable cost is still lacked. The reason is that the concentrated emulsion system is complex, has a plurality of components and interferes with each other; the system viscosity is high; the oil-dispersibility enhancing agent is high in production cost. Considering that most of the commercially available reinforcing microparticles such as silicon dioxide, titanium dioxide, iron oxide, bentonite, graphene oxide, microcrystalline cellulose, silsesquioxane and the like have water dispersibility, they can be directly used in an oil-in-water type concentrated emulsion, which means that it is particularly advantageous to prepare a porous functional material using the oil-in-water type concentrated emulsion. However, the surface of the porous material prepared by the oil-in-water concentrated emulsion method is oleophilic, and an aqueous system such as water treatment, an aqueous catalytic system and the like is difficult to use.

Patent CN106902613A discloses amino-functionalized porous CO₂The preparation method of the adsorption material comprises the steps of premixing a porous material, a certain amino modifier and a dispersant in a high-speed stirring mixer; then feeding the premixed porous material into a high-speed ultrafine grinder for full shearing, grinding, mixing and dispersing to obtain a uniformly mixed porous composite material; finally, will obtainThe porous material is dried in an oven, so that the modifier and the porous material are fully reacted to obtain the amino-functionalized porous adsorption material. The process flow of the invention is complex, the reaction may be insufficient, the material structure is not uniform, and the application range of the prepared porous material is limited.

Disclosure of Invention

The invention aims to solve the problems and provide an amino functionalized porous material, and a preparation method and application thereof.

The purpose of the invention is realized by the following technical scheme:

a preparation method of an amino functionalized porous material comprises the following steps: dispersing rigid particles into a water phase containing polyethyleneimine, adjusting the pH to 10-13, adding an oil phase to form an oil-in-water emulsion, adding the oil phase in advance or adding a cross-linking agent after the oil-in-water emulsion is formed, carrying out cross-linking reaction, standing for solidification, deoiling, dehydrating and drying after the reaction is finished, thus obtaining the product.

Preferably, the polyethyleneimine is a flexible branched molecule with the molecular weight of more than 1000, and the concentration of the polyethyleneimine in the water phase is 0.01-0.20 g/mL. Further preferably, the polyethyleneimine is a flexible branched molecule with a molecular weight of more than 10000, and the concentration of the polyethyleneimine in the aqueous phase is 0.1 g/mL.

Preferably, the rigid particles are water-dispersible materials and are selected from one or more of microcrystalline cellulose, silicon dioxide, titanium dioxide, iron oxide, graphene oxide, hydrophilic carbon nanotubes, bentonite, diatomite, kaolin or silsesquioxane, and the particle size of the rigid particles is between tens of nanometers and hundreds of micrometers.

Preferably, the oil phase is selected from one or more of toluene, cyclohexane or petroleum ether.

Preferably, the cross-linking agent is a diglycerol ether-terminated difficultly hydrolyzed compound or a dialdehyde compound with hydrophilicity, has a molecular weight not higher than 6000, and is selected from polypropylene glycol diglycerol ether, polyethylene glycol diglycerol ether or glutaraldehyde.

Preferably, the rigid particles are used in an amount of 8-60% by dry weight of the final product, and the volume of the oil phase is 50-81% of the total volume of the emulsion.

Preferably, the standing solidification is carried out at room temperature for 6-48 hours, and the porous material is mashed to be deoiled, dehydrated and dried after standing, and the specific method is as follows: washing with ethanol, vacuum drying, or adding cyclohexane and/or toluene for azeotropic dehydration, distilling to remove oil, and vacuum drying.

The application of the amino functionalized porous material in adsorption comprises adsorption of anionic dye in water, adsorption of acid gas and aldehydes and high-efficiency adsorption of metal cations after chemical modification.

(1) The porous material is directly used for adsorbing the anionic dye in water. The porous material is directly put into the wastewater containing the anionic dye, and the pH value is adjusted to be about 7 and is generally not higher than 9. It may be allowed to stand or stirred. The dye waste water gradually fades. For the dye with smaller size, the adsorption is generally completed within 3-5 days, and for the dye with larger size, the adsorption is generally completed within about 10 days. When the pH is raised above 11, the adsorbed dye may be released. The specific release rate depends on the size of the dye, the release amount of the small-sized dye such as methyl orange can reach about 70 percent, and the release amount of the large-sized dye such as Congo red is about 30 percent. The adsorbent can be used repeatedly.

(2) The porous material can be used for adsorbing acid gas and aldehydes. The material (containing bound water) is placed in an atmosphere of sulfur dioxide, carbon dioxide, nitrogen dioxide or hydrogen sulfide and the weight of the adsorbent is increased. Carbon dioxide can be reversibly released by heating after the carbon dioxide is adsorbed; other acid gases can be removed by alkali washing; adsorption of aldehydes is generally not followed by regeneration.

(3) The porous material can adsorb metal cations more efficiently after chemical modification. The porous material is dispersed in an alkaline aqueous solution (pH adjusted to 11) of chloroacetic acid (or other haloacetic acids) or a buffer solution (pH 7.4) in an amount of 1-3 molar equivalents of the amino hydrogen, and then stirred at 70-80 ℃ for more than 8 hours. Chloroacetic acid is converted into aminopolycarboxylic acid under the alkaline condition, and the aminopolycarboxylic acid can efficiently adsorb trace heavy metal ions or calcium and magnesium ions in water under the condition that the pH is close to neutral. Filtering and collecting the adsorbent, treating with acidic water (pH is less than or equal to 2), releasing a large amount of metal ions, and regenerating the adsorbent.

An application of amino functionalized porous material on metal catalyst load. Mixing the metal ion precursor and the porous material in water, and adding a reducing agent if necessary to obtain metal nanoparticles to obtain the supported catalyst. The catalyst is suitable for catalysis in polar, including aqueous phase environment, and can be used repeatedly.

The principle of the invention is that the active amino functionalized porous material is prepared by an oil-in-water type concentrated emulsion method. The core of the invention lies in the utilization of the multiple functions of polyethyleneimine. In the invention, the polyethyleneimine is used as a stabilizer of the concentrated emulsion, is also used as a flexible component of the matrix to be compounded with the reinforcing agent, and can be finally used as a carrier to express a large amount of active amino on the surface of the porous material. Due to the adoption of a proper crosslinking mode, the polyethyleneimine finally exists in a covalent network structure, does not physically fall off, does not generate acid-base induced bond breakage, and provides guarantee for repeated use. For convenience, fig. 1 is provided to aid in the description of the improved concepts of the present invention.

In FIG. 1, oil droplets are densely arranged in a water continuous phase as a dispersed soft template, a polyethylene imine component contained in water is used as a stabilizer to stabilize a concentrated emulsion, and water dispersible particles used as a mechanical reinforcing agent are simultaneously present in the water phase. In FIG. 1, the inside of the hexagon represents oil droplets, the outside of the hexagon represents water phase, water-dispersible mechanical enhancement particles are added into the water phase, the interface is expressed by polyethyleneimine, and the pH is about 11. Polyethyleneimines typically contain hundreds to thousands of repeating units, but only a dozen are drawn here for simplicity. To cure the aqueous phase, a cross-linking agent may be dissolved in the oil phase, which gradually diffuses into the aqueous phase and cross-links the polyethyleneimine. When the solubility of the cross-linking agent in oil is low, the cross-linking agent can be added into the water continuous phase after the formation of the emulsion, and the mixture is stirred uniformly and is kept stand for solidification. The polyethyleneimine plays multiple roles in practice, namely, the polyethyleneimine stabilizes oil-in-water concentrated emulsion, is used as a flexible component to be compounded with a solid particle reinforcing agent to improve the mechanical strength, and provides active amino groups. The polyethyleneimine has the characteristics that the polyethyleneimine has high-density active amino groups, the branched structure of the polyethyleneimine enables the viscosity of an aqueous solution of the polyethyleneimine to be very low, and the polyethyleneimine can present amphipathy under high pH.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the polyethyleneimine adopted by the invention is of a branched structure, the viscosity of the aqueous solution is low, and the viscosity of the mixed polyethyleneimine with rigid particles is still quite low, so that the production is convenient.

(2) Generally, the volume of the dispersed phase in the emulsion is more than 74 percent of the volume of the whole system, so that the porous material is easy to form, but the porous material can be formed even if the volume is as low as 50 percent in the invention, which is beneficial to improving the mechanical property of the material.

(3) The invention has simple production process, and can directly utilize the existing mechanical equipment to prepare the active amino-functionalized porous material with better mechanical strength.

(4) The porous material can be directly used for water treatment, acid gas adsorption and gas separation, and can efficiently adsorb Cu after further modification²⁺，Cr³⁺，Ni²⁺，Pb²⁺，Mn²⁺，Zn²⁺，Co²⁺And the residual rate after adsorption is low when cations or calcium and magnesium ions are used. The adsorbent is acid and alkali resistant and can be used repeatedly.

Drawings

FIG. 1 is a schematic diagram of a process for preparing a porous material according to the present invention;

FIG. 2 is a scanning electron micrograph of the porous material of the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples 1 to 12 relate to the preparation of porous materials, and examples 13 to 16 relate to the use of porous materials.

Example 1

Microcrystalline cellulose (0.06g) was added to branched polyethyleneimine (M)_n＝60 000，0.1g/mL，1mL) The aqueous dispersion of (3) was stirred and dispersed, pH was adjusted to 11, cyclohexane (2.5mL) was added dropwise to the aqueous dispersion with vigorous stirring, and after dropping over 6 minutes, polyethylene glycol diglycerol ether (M) was added to the system_n500, 0.29g, 0.25 eq of NH), stirring was continued for 1 minute, and allowed to solidify for 6 hours. 20 ml of cyclohexane was added to the system, followed by heating under reflux and separation of most of the water with a decanter, followed by distillation of cyclohexane and vacuum drying of the remaining solid to give a porous material (see FIG. 2).

Example 2

The same as example 1, but replacing cyclohexane by petroleum ether. And standing for 24 hours, mashing the condensate, washing with ethanol, and drying in vacuum to obtain the porous material.

Example 3

Microcrystalline cellulose (0.06g) was added to a mixture containing branched polyethyleneimine (M)_n60000, 0.1g/mL, 1mL) was stirred and dispersed, the pH was adjusted to 11, and toluene (4.2mL) and polypropylene glycol diglycerol ether (M) were added dropwise to the aqueous dispersion with vigorous stirring_n380, 0.22g, 0.25 eq of NH) was added dropwise over 10 minutes, stirring was continued for 2 minutes, and the mixture was left to stand for 24 hours. And (4) mashing the solid, washing with ethanol, and drying in vacuum to obtain the porous material.

Example 4

Microcrystalline cellulose (0.06g) was added to a mixture containing branched polyethyleneimine (M)_n60000, 0.1g/mL, 1mL) and graphene oxide (TCI product, 10mg/mL, 0.4mL) were added dropwise to an aqueous dispersion of toluene (4.2mL) and polypropylene glycol diglycerol ether (M) under vigorous stirring, followed by stirring and dispersing to adjust the pH to 11_n380 g, 0.22g, 0.25 eq of NH), the solution was added dropwise over 10 minutes, stirred for 2 minutes and allowed to stand for 12 hours. And (4) mashing the solid, washing with ethanol, and drying in vacuum to obtain the porous material.

Example 5

Similar to example 3, but reduce the volume of toluene to 1.5ml, similar to the procedure. A porous material was also obtained.

Example 6

Microcrystalline cellulose (0.04g) was added to the solutionBranched polyethyleneimines (M)_n60000, 0.1g/mL, 1mL), the aqueous dispersion was stirred and dispersed, the pH was adjusted to 11, and cyclohexane (1.5mL) was added dropwise to the aqueous dispersion with vigorous stirring, and the solution was dropped over 5 minutes. Then adding polypropylene glycol diglycerol ether (M) in one portion_n380, 0.22g, 0.25 eq of NH), stirring was continued for 1 minute and allowed to stand for 6 hours. 10 ml of cyclohexane was added to conduct azeotropic dehydration, followed by distilling off cyclohexane and vacuum drying to obtain a porous material.

Example 7

In a similar manner to example 3, but with the same weight of diatomaceous earth in place of microcrystalline cellulose, a porous material was obtained.

Example 8

In a similar manner to example 3, but with the same weight of bentonite instead of microcrystalline cellulose, a porous material was obtained.

Example 9

Similar to example 1, but with the microcrystalline cellulose content reduced to 0.03 g, a softer, more elastic porous material was obtained.

Example 10

Similar to example 1, but with the amount of polypropylene glycol diglycerol ether reduced to 0.14 g, a softer, more resilient porous material was obtained.

Example 11

Silica (0.02g) and titanium dioxide (0.04g) were added to a mixture containing branched polyethyleneimine (M)_n60000, 0.01g/mL, 4mL), the mixture was stirred and dispersed, the pH was adjusted to 10.5, and cyclohexane (1.5mL) and toluene (2.5mL) were added dropwise to the aqueous dispersion with vigorous stirring, and the solution was dropped over 5 minutes. And then adding glutaraldehyde at one time, continuing stirring for 1 minute, standing for 24 hours, mashing the solid, washing with ethanol, and drying in vacuum to obtain the porous material.

Example 12

Kaolin (0.05g) was added to a mixture containing branched polyethyleneimine (M)_n60000, 0.2g/mL, 2mL) was stirred and dispersed, the pH was adjusted to 12.5, and toluene (1mL) and petroleum ether (3mL) were added dropwise to the aqueous dispersion under vigorous stirring, and dropwise addition was carried out within 5 minutesAnd finishing. And then adding glutaraldehyde at one time, continuing stirring for 1 minute, standing for 24 hours, mashing the solid, washing with ethanol, and drying in vacuum to obtain the porous material.

Example 13

In rose bengal solution (0.5X 10)^-4M, 5ml) was added to the porous material (prepared in example 1) (0.2 g), and left to stand for 8 days or stirred for 5 days. The water faded and the absorbance at 546nm was reduced to 0.002 (equivalent to 2.2X 10) as measured by UV/vis spectroscopy^-8M)。

Example 14

The porous material (prepared in example 3) was placed in a gas cylinder filled with carbon dioxide or sulfur dioxide and left for 6 hours, and then taken out and weighed, and the weight of the porous material was found to increase, with the weight gain being 1-5%.

Example 15

A porous material was prepared according to the formulation of example 3 at 10 x magnification. Taking 1.85 g of the amino polycarboxylic acid modified porous material, adding chloroacetic acid (3.96 g) and potassium carbonate (5.80 g) aqueous solution (50 ml), stirring at 75 ℃ for 27h, filtering and washing to obtain the amino polycarboxylic acid modified porous material.

Example 16

And (4) adsorbing metal ions. Separately preparing Co²⁺，Pb²⁺，Cd²⁺，Ni²⁺The initial concentrations of the stock solutions of (1) are shown in Table 1. 5.5 ml of the stock solution was taken, 35 mg of the porous material obtained in example 13 was added thereto, and after 1 hour, the filtrate was filtered through a common filter paper, and the metal residue in the filtrate was measured by inductively induced plasma spectroscopy (ICP-ms), and the result was as shown in Table 1, and the metal residue was low.

TABLE 1 adsorption of several metal ions (unit: ppm) by the adsorbent in example 16, pH 7.0.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A preparation method of an amino functionalized porous material is characterized by comprising the following steps: dispersing rigid particles into a water phase containing polyethyleneimine, adjusting the pH to 10-13, adding an oil phase to form an oil-in-water emulsion, adding the oil phase in advance or adding a cross-linking agent after the oil-in-water emulsion is formed, carrying out cross-linking reaction, standing for solidification, deoiling, dehydrating and drying after the reaction is finished, thus obtaining a product;

the rigid particles are water-dispersible substances and are selected from one or more of microcrystalline cellulose, silicon dioxide, titanium dioxide, ferric oxide, graphene oxide, hydrophilic carbon nanotubes, bentonite, diatomite, kaolin or silsesquioxane, and the particle size of the rigid particles is between several nanometers and hundreds of micrometers.

2. The preparation method of the amino-functionalized porous material according to claim 1, wherein the polyethyleneimine is a flexible branched molecule with molecular weight more than 1000, and the concentration of the polyethyleneimine in the water phase is 0.01-0.20 g/mL.

3. The preparation method of the amino-functionalized porous material according to claim 2, wherein the polyethyleneimine is a flexible branched molecule with molecular weight greater than 10000, and the concentration of the polyethyleneimine in the aqueous phase is 0.1 g/mL.

4. The method for preparing amino-functionalized porous material according to claim 1, wherein the oil phase is selected from one or more of toluene, cyclohexane or petroleum ether.

5. The method for preparing an amino-functionalized porous material according to claim 1, wherein the cross-linking agent is a hydrophilic diglycerol ether-terminated difficultly-hydrolyzed compound or a dialdehyde compound, and is selected from polypropylene glycol diglycerol ether, polyethylene glycol diglycerol ether or glutaraldehyde.

6. The method for preparing amino functionalized porous material according to claim 1, wherein the amount of the rigid particles is 8-60% of the dry weight of the final product, and the volume of the oil phase is 50-81% of the total volume of the emulsion.

7. The preparation method of the amino-functionalized porous material according to claim 1, wherein the standing solidification is performed at room temperature for 6-48 hours, and after standing, the porous material is smashed and deoiled, dehydrated and dried, and the method comprises the following specific steps: washing with ethanol, vacuum drying, or adding cyclohexane and/or toluene for azeotropic dehydration, distilling to remove oil, and vacuum drying.

8. A porous material obtained by the method for preparing an amino-functionalized porous material according to any one of claims 1 to 7.

9. Use of a porous material according to claim 8 for adsorption of anionic dyes, acid gases, metal catalyst loading or metal cations in water.